The measurement of the flow velocity of fluids in pipelines, and the corresponding measurement of the delivery rate, is usually based on the laws of the mechanics of fluids which govern the reactions between a moving fluid and a measuring device (such as a Venturi, vane wheel or the like). Sometimes, marker elements are used, which travel with the fluid, such as floats on a stream of water, and the transit time of this element over a reference distance is determined. These measurements, which are simple in principle, in general only give approximate results.
The velocity of flow of fluids has been measured by determining the velocity of particles by the Doppler effect of a coherent light beam reflected from these particles. These measurements are precise but employ expensive apparatus and, in particular, precision optical devices.
The present invention relates to a process for measuring the flow velocity of a fluid which employs marking elements and which gives a precision comparable to that of the usual measurements which make use of the mechanics of fluids, whilst remaining simple and inexpensive.
The invention also relates to such a process of measurement, where the marking element is produced from the fluid itself.